How to Repair Cracks in Concrete

Did the freezing-thawing-freezing of winter ice create cracks in your concrete? There’s no need to replace the entire offending area: thanks to  BLACK+DECKER™ Complete Photo Guide to Home Repair, you can easily fill the cracks. (As always, we know you know this, but here’s a reminder: be smart about your safety with this and all DIY work. Wear safety goggles, gloves, and a mask when repairing concrete.)

The materials and methods for repairing cracks in concrete depend on the location and size of the crack. For small cracks (less than ¼” wide), you can use gray‑tinted concrete caulk for a quick fix. For more permanent solutions, use pourable crack filler or fortified patching cements. The patching cements are polymer compounds that increase the bonding properties and allow some flexibility. For larger cracks on horizontal surfaces, use fortified sand‑mix concrete; for cracks on vertical surfaces, use hydraulic or quick‑setting cement. Thorough preparation is essential for creating a good bonding surface.

caulkUse concrete repair caulk for quick‑fix repairs to minor cracks. Although convenient, repair caulk should be viewed only as a short‑term solution to improve appearance and help prevent further damage from water penetration. Photo credit: BLACK+DECKER The Complete Photo Guide to Home Repair, 4th edition

Tools & Materials:

  • Wire brush
  • Drill with wire wheel attachment
  • Stone chisel
  • Hand maul
  • Paint brush
  • Trowel
  • Latex bonding agent
  • Work gloves
  • Vinyl‑reinforced patching compound
  • Concrete caulk
  • Fortified sand‑mix concrete
  • Plastic sheeting
  • Pourable crack filler
  • Hydraulic or quick-setting cement

Tips for Preparing Cracked Concrete for Repair

brushPhoto credit: BLACK+DECKER The Complete Photo Guide to Home Repair, 4th edition

1  Clean loose material from the crack using a wire brush or a portable drill with a wire wheel attachment. Loose material or debris left in the crack will result in a poor bond and an ineffective repair.

chiselPhoto credit: BLACK+DECKER The Complete Photo Guide to Home Repair, 4th edition

2  Chisel out the crack to create a backward‑angled cut (wider at the base than at the surface), using a stone chisel and hammer. The angled cutout shape prevents the repair material from pushing out of the crack.

How to Repair Small Cracks in Concrete

step1Photo credit: BLACK+DECKER The Complete Photo Guide to Home Repair, 4th edition

1  Prepare the crack for the repair (mentioned above), then apply a thin layer of latex bonding agent to the entire repair area, using a paint brush. The latex bonding agent helps keep the repair material from loosening or popping out of the crack.

step2Photo credit: BLACK+DECKER The Complete Photo Guide to Home Repair, 4th edition

2  Mix vinyl‑reinforced patching compound, and trowel it into the crack. Feather the repair with a trowel, so it is even with the surrounding surface. Cover the surface with plastic and protect it from traffic for at least a week.

Variations for Repairing Large Cracks in Concrete

step3Photo credit: BLACK+DECKER The Complete Photo Guide to Home Repair, 4th edition

Horizontal surfaces: Prepare the crack (mentioned above), then pour sand into the crack to within ½” of the surface. Prepare sand‑mix concrete, adding a concrete fortifier, then trowel the mixture into the crack. Feather until even with the surface, using a trowel.

step4Photo credit: BLACK+DECKER The Complete Photo Guide to Home Repair, 4th edition

Vertical surfaces: Prepare the crack (mentioned above). Mix vinyl‑reinforced concrete or hydraulic cement, then trowel a ¼”- to ½”-thick layer into the crack until the crack is slightly overfilled. Feather the material even with the surrounding surface, then let it dry. If the crack is over ½” deep, trowel in consecutive layers. Let each layer dry before applying another.

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